Thursday, July 26, 2012

Over the last 20 years, I have taken many nature photos –
usually of cool critters in cool places. I had posted a few on my website but
never had the time to keep it up to date. Nonetheless, people would see them
and want to see more. Then I would have to dig through all of my files to find
other ones I thought they might be interested in. Each time I did this, I would
tell myself that I really should put them up all on line so that anyone could
peruse them all.

I have organized them into two “collections” – one of cool places and one of cool critters. The latter is a subset of the former – having excluded non-critter photos. All of them were uploaded in the original size and can be downloaded in that original size or smaller versions thereof.

The photos are free for non-profit use and reasonably priced if used for profit. Just contact me for permission in either case.

Friday, July 20, 2012

Last week I was at the Evolution 2012 meeting in Ottawa. A
joint meeting of five evolution and ecology societies, it was the largest
collection of evolutionary biologists (plus some ecologists) ever assembled in
a single place. It was an incredibly dynamic and exciting meeting with tons of
opportunity for discussion and argument lubricated with appropriate – if expensive
– beverages. Two presentations in particular, keynote addresses of a sort,
stimulated a series of arguments that led to the reflections contained in this
post.

UBC biologist Rosie Redfield gave a public outreach talk
that detailed the debacle surrounding a paper published in Science where a
bunch of NASA scientists claimed to have found bacteria that could construct
their DNA backbone with arsenate rather than phosphorous. If true, this would
have incredible implications for our understanding of life on earth and beyond.
Rosie had read this paper and written in her research blog (http://rrresearch.fieldofscience.com/)
about how horrible it was – stated simply, the work was far from providing the standard
of evidence necessary for the inferences it was attempting to make. Rosie
quickly became a scientific icon of the blogosphere for her withering
criticisms of the paper. Rosie then redid the studies with the proper standards
and showed that the original result didn’t hold – all organisms do in the end probably
use phosphorus. Rosie’s paper was also published in Science – and it appeared
online precisely in the middle of her talk, which was not a coincidence. It has been said that “negative reviews often give
a frisson of pleasure the reader” (Houle 1998 - Evolution) and so do negative
talks to the listener – at least to many of them.

The other “keynote” I want to mention was the performance by
Baba Brinkman of his “Rap Guide to Evolution.” I had known of, and greatly
appreciated, this work of science/art/poetry/music for a few years but this was
the first time I had seen it in person. In addition to giving great
performances of some of the work I already knew of, he had some new – and equally
hilarious and insightful – stuff (Don’t
Sleep with Mean People was a highlight). Everyone should hear and see Baba’s
work: http://www.bababrinkman.com/.
Coincidentally, I happened to run into Baba during one of the mixers and also
at bars on two other nights, which formed the second inspiration for this blog
about standards of evidence.

Baba dropping an evolutionary rap anthem.

Baba’s work summarizes in entertaining and generally correct
form many of the basic underpinnings – and also unique nuances – of evolutionary
biology. He also strays into evolutionary psychology. Although prefacing his
dialog with a disclaimer that much of the field might well be bunk, he is
clearly a fan – even if only because of how it makes one think about human
behavior. His favorite example is the correlation
among human communities between mortality rates and teen pregnancy rates (and
other things). He explains in a rapid rap flow the hypothesis of Daly and
Wilson (1988) about how it makes evolutionary sense to reproduce early if your
mate is likely to die soon. In short, teen pregnancy might be an adaptive
reproductive strategy (or tactic) in response to high-risk situations. The
graph relating mortality rates (x-axis) to teen pregnancy (y-axis) is extremely
strong; indeed, it would be the envy of most empirical evolutionary biologists
working on any organism. But (to continue the point of my previous post on
Faith’s Conjecture: http://ecoevoevoeco.blogspot.ca/2012/07/faiths-conjecture.html)
how can we be sure this is a causal relationship. Perhaps high teen pregnancy
rates (x-axis) lead to fathers adopting riskier and more aggressive strategies
that increase mortality rates (y-axis). Or maybe both phenomena are
independently driven by some external factor. What standard of evidence would
be necessary to make this conclusion with surety?

In my conversation with Baba, he argued that work on humans
should be held to the same standard of evidence as work on other organisms.
With other organisms, however, we would perform experiments. We would alter
mortality rates and see if it changed the age of reproduction. Indeed just such
experiments have been done: when guppies are introduced from high-mortality
environments to low-mortality environments they evolve delayed reproduction
(and vice versa). But we can’t do this sort of controlled experiment with
humans, of course. So we clearly can’t hold work on humans to the same standard
of evidence – but we should push as far as possible. Or should we?

In 1999, I was in the audience for a symposium called “Darwinian
Evolution Across Disciplines” held at Dartmouth College. A collection of
speakers from a variety of disciplines (religious studies, anthropology, medicine,
etc.) spoke about how evolutionary thinking had influenced their disciplines. (The
representative real evolutionary biologist, Dick Lewontin, spoke about cosmic
evolution – go figure.) At the end of the symposium, all of the speakers lined
up their chairs at the front of the room and the audience was allowed to ask
questions. My question started with the preface that evolutionary biologists were
heavily criticized (by Dick) for telling “just so stories” to explain the adaptive
significance of trait variation. (That is, inferences weren’t based on an
appropriate standard of evidence.) I then noted out loud that it seemed like
most of these other disciplines were still in the “just so” phase, and I asked
what the prospects were for transitioning into the rigorous hypothesis testing now
employed in evolutionary biology. A few speakers gave some comments and then
one of them turned to Dick, who had not yet spoken, and asked something like “What
do you think Dick?” After pausing for effect, he turned to face all of the
other speakers and said something like “I don’t think that any of you know how
evolutionary biology works.” And then he went on to disparage their fields for
a few minutes before turning to me and saying that he still felt evolutionary
biology was in the “just so” phase. Then he walked out. Frisson! (A video
exists of Dick chastise us [although I can’t seem to access it right now]: http://www.dartmouth.edu/~dead99/Disc/Disc.htm.
)

The lesson I think we should take from all this arguing and
frissing is that we should push evolutionary psychologists to base their
inference on the highest possible standard of evidence THAT IS APPROPRIATE FOR
WHAT IS POSSIBLE. That is, we simply can’t perform evolutionary experiments on
humans. We need to find some happy point between Baba Brinkman and Dick
Lewontin – probably a lot closer to the former than the latter.

And, of course, we should strive for exactly the same thing in
evolutionary biology in general: the highest possible standard of evidence. But
striving is different from achieving, and so it is reasonable to ask should we
also HOLD evolutionary biologists to those standards – by, for example, blocking
the publication of studies that don’t perform manipulative experiments in
nature or that don’t use the latest genetic methodologies? I don’t think so.
First, incredible inequities exist in the manipulability and genetic resources
for different taxa. We simply can’t expect people who work on mosquitofish and walkingsticks
to deploy the same genetic tools as people who work on flies or mice or
stickleback or humans. And we can’t expect people who work on elephants or
hippos or albatrosses or humans to perform the manipulative evolutionary
experiments typical of flies and mice and bacteria. This doesn’t mean that we
should all work on those “ideal” model systems – we really do need to study the
full pageantry of life. The solution then must be to hold work on a given taxon
to the highest possible standards for that taxon – standards must be scaled to
taxa.

Or is that really the case? Can we really expect everyone who
works stickleback to fully sequence all the individuals in their study
populations? Can we really expect everyone who works on guppies to perform
manipulative evolutionary experiments? Clearly not, as the resources and opportunities
to do so are out of reach of most people working even on these groups. Thus, we
can’t apply a particular standard of evidence to all papers from a given
taxonomic group – even in Science and Nature! Otherwise, we are always chasing
the latest technology or the most money or the biggest collaborations – and we
are saying, in essence, that work published just a few years earlier would not
be worth publishing in the same form today. This is nonsense. The major
advances in evolutionary biology were ideas – and ideas are what stand the test
of time (V!). So I would encourage all of us, whether acting as authors or
reviewers or editors or bloggers or rappers to strive for the highest possible
standards of evidence in our own work while also judging the work of others
according to what is reasonable and possible for them – and to what extent
their ideas are interesting and stimulating. (Just think how much less exciting
the last year would have been without those NASA scientists.) We need to find some
happy place between Baba Brinkman and Dick Lewontin.

Just recently, I spent a week in Bonito, Brazil, for the
annual meeting of the bioGENESIS core project for DIVERSITAS. Over dinner, we
strayed into rules, laws, paradoxes, and conjectures: which one we wanted to
have and what it would be. Dan Faith decided that he wanted a Conjecture – and
proceeded to suggest one. He proposed that any fairy tale or fable could be
inverted so that its message would change in an interesting and informative
way. Take, for example, the tortoise and the hare. Maybe the tortoise had heard
the classic fable and so assumed he would win, thus losing owing to arrogance
or inattentiveness. Or maybe the hare had heard it and so realized he would
lose if he didn’t run steadily. Tortoise loses – hare wins – lesson changes:
those who don’t pay attention to history are bound to repeat it. Having
succeeded here, we tried a few other fairy tales and fables on the Conjecture
and I have to confess it was a bit of a force to make it work. Time to give up on Faith's Conjecture.

A few days later, however, I got to thinking about it a bit
more and realized that perhaps Faith’s Conjecture really was valid – but in a
different context: ecology and evolution. I hereby restate Faith’s Conjecture
as: any correlation from which a causal relationship might be inferred (the thing on
the x axis influences the thing on the y axis) can be inverted (the things on
the x and y are switched) to lead to a new causal inference. Here are some
examples.

Gene flow is often assumed to constrain adaptive divergence.
Thus, one would expect that populations experiencing higher levels of gene flow
would show lower adaptive divergence. So one goes out in nature, samples a
bunch of independent population pairs, and tests whether pairs that are more
divergent in adaptive traits (y axis) are also those showing lower gene flow (x
axis). If such a correlation is present, one infers that gene flow constrains
adaptive divergence. However, it is also true that adaptive divergence might
constrain gene flow. This is the hypothesis of ecological speciation, where
increasing adaptive divergence causes greater ecologically-based reproductive
barriers, which decrease gene flow. So one goes out in nature, samples a bunch
of independent population pairs, and tests whether pairs that are more
divergent in adaptive traits (now the x axis) are also those that show lower
gene flow (now the y axis). If the correlation is present, one infers that
adaptive divergence reduces gene flow: ecological speciation! Thus, the exact
same correlation can be inverted for two different inferences. Remarkably this
example is real: many studies have plotted gene flow on the x axis and adaptive divergence on the y axis and made the first inference while many other studies have
plotted adaptive divergence on the y axis and gene flow on the x axis and made the second inference. Faith’s Conjecture in the machine!

A perennial topic in biodiversity science is the idea that
increasing biodiversity (e.g., number of species) increases ecosystem
productivity. This makes sense because, among several reasons, more species
will presumably use a more diverse set of resources and thereby increase the
overall productivity of the system. So one goes out in nature, samples a bunch
of plots, and shows that plots with higher biodiversity have higher
productivity: hypothesis validated - we need to save more biodiversity because it
will increase productivity, a key ecosystem service. But, at the same time, it
has long been known that increased productivity can increase biodiversity – at
least up to a point. After all, higher productivity allows more total
individuals in an ecosystem which increases both the width and depth of, and
thus the number of species in, the food web. So one goes out in nature … you get
the idea.

Many other examples exist – and, importantly, every one of
these has been inferred in correlational studies. Smaller species' ranges should
obviously lead to less genetic diversity, since smaller population sizes and
adaptation to a narrow range of conditions should lead to the depletion of
genetic diversity. Yet on the flip side, less genetic diversity should
constrain evolutionary potential and thus lead to smaller species ranges. Increased
diet diversity within a population leads to increased trophic trait diversity
owing to disruptive selection, but increased trophic trait diversity leads to
increased diet diversity because individuals with different traits can feed on
different foods. Etc. Etc. Ad infinitum.

So, Faith’s Conjecture is upheld. Perhaps it is even a law
or a rule but, for my money, I would rather have a conjecture too. It just sounds
cooler- and easier! I should point out that Faith’s Conjecture cannot be directly tested
simply through logic of the above sort. Instead, one needs to experimentally
manipulate each of the axes to see if it really does causally effect the other
axis and, interestingly, this has been done – and confirmed – in the above examples.
In addition, Faith’s Conjecture does not necessarily apply to situations where one
of the axes is not a biological variable. For example, increasing geographical
distance decreases gene flow but increasing gene flow does not decrease
geographical distance.

I propose the Faith’s Conjecture is commonly – perhaps universally
– true, and I challenge the reader to provide putative instances where it succeeds
or fails. In the latter case, I intend to either prove that cause and effect
really are reversible in the proffered example or that the example does not apply. In
short, I hope to redefine Faith’s Conjecture as necessary so that it conveniently excludes
examples that do not abide. After all, the next best thing to having one's own conjecture is to be the person to name the conjecture.

Lots of other cool stuff in the Carnival too! I've been enjoying wrapping my brain around all the controversy surrounding group selection and kin selection, and there are several posts on that; but a dozen or two other posts, too.

It being the Mousetrap, they chose an animal trap theme for this month. Well, it's hard to fit these themes sometimes, but here's Andrew catching fish (probably guppies):